Mazda RX-7

RX7The Mazda RX-7 is a sports car that was produced from 1978 to 2002. It featured a twin-rotor Wankel rotary engine and a front-midship, rear-wheel drive layout. The RX-7 replaced the RX-3, with both models sold in Japan as the Mazda Savanna.

The compact and lightweight Wankel rotary engine is situated slightly behind the front axle, a configuration marketed by Mazda as “Front Mid-Engine”. It was built as a two seat coupe, with a dealer-installed option available in North American Markets to include rear seats.

This unique coupe made the Car and Driver magazine’s Ten Best list five times and was also available as a convertible.

RX7First Generation (SA22C/FB) (1978-1985)

Series 1 (1978–1980) is commonly referred to as the “SA22C” from the first alphanumerics of the vehicle identification number. In Japan it was introduced in March 1978, replacing the Savanna RX-3.

The transition of the Savanna sedan design to a sports car appearance reflected products from other Japanese manufacturers. The advantage the RX-7 had was its minimal size and weight. The compact rotary engine installed behind the front axle helped balance the front to rear weight distribution and provide a low center of gravity.

In Japan, sales were enhanced by the fact that the RX-7 complied with Japanese Government dimension regulations, and Japanese buyers were not liable for yearly taxes for driving a larger car. The rotary engine displacement remained below 1.5 liters, a significant determination when paying the Japanese annual road tax which kept the obligation affordable to most buyers, while having more power than the traditional inline engines.

RX7The Series 2 (1981–1983) had integrated plastic-covered bumpers, wide black rubber body side moldings, wraparound taillights and updated engine control components. While marginally longer overall, the new model was 135 lb lighter. The four-speed manual option was dropped for 1981 as well, while the gas tank grew larger and the dashboard was redesigned, including a shorter gear stick mounted closer to the driver. The GSL package provided optional four-wheel disc brakes and clutch-type rear limited slip differential (LSD).

RX7The Series 3 (1984–1985) featured an updated lower front fascia. North American models received a different instrument cluster. GSL package was continued into this series, but Mazda introduced the GSL-SE sub-model. The GSL-SE had a fuel-injected 1.3L engine producing 135 hp and 135 lb·ft torque. GSL-SEs had much the same options as the GSL (clutch-type rear LSD and rear disc brakes), but the brake rotors were larger, allowing Mazda to use lug nuts instead of bolts, and a new bolt pattern of 4×114.3. They had an upgraded suspension with stiffer springs and shocks and an external oil cooler was reintroduced, after being dropped in the 1983 model-year for a controversial “beehive” water-oil heat exchanger.

The 1984 RX-7 GSL has an estimated 29 highway miles per gallon and 19 estimated city miles per gallon. According to Mazda, its rotary engine, licensed by NSU-Wankel allowed the RX-7 GSL to accelerate from 0 to 50 in 6.3 seconds.

The handling and acceleration of the car were noted to be of a high caliber for its day. This was achieved by the combination of a live-axle 4-link rear suspension with Watt’s linkage, a 50/50 weight ratio, and it weighed under 2,500 lb. This was the lightest generation of RX-7 ever produced. 12A-powered models accelerated from 0–60 mph in 9.2 seconds, and turned 0.779 g laterally on a skidpad. The 12A engine produced 100 hp at 6,000 rpm, allowing the car to reach speeds of over 120 miles per hour. Because of the smoothness inherent in the Wankel rotary engine, very little vibration or harshness was experienced at high engine speeds, so a buzzer was fitted to the tachometer to warn the driver when the 7,000 rpm redline was approaching.

12AThe 12A engine has a long thin shaped combustion chamber, having a large surface area in relation to its volume. Therefore, combustion is cool, giving few oxides of nitrogen. However, the combustion is also incomplete, so there are large amounts of partly burned hydrocarbons and carbon monoxide. The exhaust is hot enough for combustion of these to continue into the exhaust. An engine driven pump supplies air into the exhaust to complete the burn of these chemicals. This is done in the “thermal reactor” chamber where the exhaust manifold would normally be on a conventional engine. Under certain conditions the pump injects air into the thermal reactor and at other times air is pumped through injectors into the exhaust ports. This fresh air is needed for more efficient and cleaner burning of the air/fuel mixture.

Savanna RX-7 Turbo
Following the introduction of the first turbocharged rotary engine in the Mazda Luce/Cosmo, a similar, also fuel injected and non-intercooled 12A turbo engine was made available for the top-end model of the series 3 RX-7 in Japan. While the peak power figures were only somewhat higher than those of the engine used in the Luce/Cosmo, the new “Impact Turbo” was developed specifically to deal with the different exhaust gas characteristics of a rotary engine. Both rotor vanes of the turbine were remodeled and made smaller, and the turbine had a twenty percent higher speed than a turbo intended for a conventional engine. The Savanna Turbo was short-lived, as the next generation RX-7 was just about to debut.

RX7Second generation (FC)
The Series 4 (1985–1988) was available with a naturally aspirated, fuel-injected 13B-VDEI producing 146 hp. An optional turbocharged model, (1985–1988) known as the Turbo II in the American market, had 182 hp.

The Series 5 (1989–1992) featured updated styling and better engine management, as well as lighter rotors and a higher compression ratio, 9.7:1 for the naturally aspirated model, and 9.0:1 for the turbo model. The naturally aspirated Series 5 FC made 160 hp, while the Series 5 Turbo made 200 hp.

RX7The second generation RX-7, still known as the Mazda Savanna RX-7 in Japan, featured a complete restyling reminiscent of the Porsche 924. Mazda’s stylists, focused on the Porsche 924 for their inspiration in designing the FC because the new car was being styled primarily for the American market, where the majority of first generation RX-7’s had been sold. The Porsche 944 was selling particularly well at the time and provided clues as to what sports-car enthusiasts might find compelling in future RX-7 styling and equipment.

While the SA22/FB was a purer sports car, the FC tended toward the softer sport-tourer trends of its day. Handling was much improved, with less of the oversteer tendencies of the FB. The rear end design was vastly improved from the FB’s live rear axle to a more modern, Independent Rear Suspension. Steering was more precise, with rack and pinion steering replacing the old recirculating ball steering of the FB. Disc brakes also became standard, with some models offering four-piston front brakes. The rear seats were optional in some models of the FC RX-7, but are not commonly found in the American Market.

Mazda also introduced Dynamic Tracking Suspension System (DTSS) in the 2nd-gen RX-7. The revised independent rear suspension incorporated special toe control hubs which were capable of introducing a limited degree of passive rear steering under cornering loads. The DTSS worked by allowing a slight amount of toe-out under normal driving conditions but induced slight toe-in under heavier cornering loads at around 0.5 G’s or more; toe-out in the rear allows for a more responsive rotation of the rear, but toe-in allowed for a more stable rear under heavier cornering. They also introduced Auto Adjusting Suspension (AAS) in the 2nd generation RX-7. The system changed damping characteristics according to the road and driving conditions. It compensated for camber changes and provided anti-dive and anti-squat effects.

RX7The Turbo 2 uses a turbo charger with a twin scroll design. The smaller primary chamber is engineered to cancel the turbo lag at low engine speeds. At higher revolutions the secondary chamber is opened, pumping out 33% more power than the naturally aspirated counterpart. The Turbo 2 also has an air-to-air intercooler which has a dedicated intake on the hood.

In the Japanese market, only the turbo engine was available; the naturally aspirated version was allowed only as an export. This can be attributed to insurance companies in many Western nations penalizing turbo cars thus restricting potential sales. This emphasis on containing horsepower and placating insurance companies to make RX-7’s more affordable seems ironic in retrospect. Shortly after the discontinuance of the second generation RX-7’s in 1992, an outright “horsepower race” broke out between sports car manufacturers, with higher and higher levels of power required to meet buyer demands. This rising horsepower phenomena arose from the US fuel economy standards remaining stable while engine technologies marched forward rapidly.

1988 Mazda RX-7 Convertible (FC)
Mazda introduced a convertible version of the RX-7 in 1988 with a naturally aspirated engine. The convertible featured a removable rigid section over the seats and a folding textile rear section with heatable rear glass window. Power operated, lowering the top required unlatching two header catches, power lowering the top, exiting the car, or reaching over to the right side latch, and folding down the rigid section manually. Mazda introduced with the convertible the first integral wind-blocker, a rigid panel that folded up from behind the passenger seats to block unwanted drafts from reaching the passengers — thereby extending the driving season for the car in open mode. The convertible also featured optional headrest mounted audio speakers and a folding leather snap-fastened tonneau cover. The convertible assembly was precisely engineered and manufactured, and dropped into the ready body assembly as a complete unit — a first in convertible production.

RX7Third generation (FD)
The third generation of the RX-7 (FD), featured an updated body design. The 13B-REW was the first-ever mass-produced sequential twin-turbocharger system to export from Japan, boosting power to 252 hp in 1993 and finally 276 hp by the time production ended in Japan in 2002.

In Japan, sales were affected by the fact that this series RX-7 no longer complied with Japanese Government dimension regulations, and Japanese buyers were now liable for yearly taxes for driving a wider car compared to previous generations.

In 1992, Mazda introduced a sequential twin turbocharged system. It was composed of two turbochargers, one to provide boost at low RPM. The second unit to provide boost in the upper half of the rpm range during full throttle acceleration. The first turbocharger provided 10 psi of boost from 1800 rpm, and the second turbocharger spooled at 4000 rpm to maintain 10 psi until redline. The changeover process occurred at 4500 rpm, with a momentary dip in pressure to 8 psi, and provided semi-linear acceleration and a wide torque curve throughout the entire rev range under “normal operation”. Under performance driving the changeover process produced a significant increase in power and forced technical drivers to adjust their driving style to anticipate and mitigate any over-steer during cornering. Many owners modified their turbo control systems into a parallel system by removing the exhaust manifold Turbo Control Valve, the turbo coupling “y-pipe” Charge Control Actuator, and valve in order to remove the changeover process and to simplify the control system for reliability. Turbo lag is greatly increased below 4500 rpm, but smooth and linear boost could be obtained. The stock turbo control system used 4 control solenoids, 4 actuators, both a vacuum and pressure chamber, and several feet of pre-formed vacuum/pressure hoses all of which were prone to failure in part to complexity and the inherent high temperatures of the rotary engine.

Series 6 (1991–1995) was exported throughout the world and had the highest sales.
In 1993, three North American models were offered; the “base”, the touring, and the R models. The touring FD included a sunroof, fog lights, leather seats, a rear window wiper and a Bose Acoustic Wave system. The R (R1 in 1993 and R2 in 1994–95) models featured stiffer suspensions, an additional engine oil cooler, an aerodynamics package, purple-hued microfiber seats, and Z-rated tires. In 1994, the interior received a small update to include a passenger air bag, and a PEG (performance equipment group) model was offered. This model featured leather seats and a sunroof; however, it did not include the fog lights or Bose stereo of the touring package. In 1995, the touring package was replaced by the PEP (popular equipment package). The PEP package contained leather seats, sunroof and fog lights, but didn’t have the Bose Stereo nor the rear window wiper.

Series 7 (1996–1998) included minor changes to the car. Updates included a simplified vacuum routing manifold and a 16-bit ECU which combined with an improved intake system netted only a few extra horsepower and this additional horsepower was only available on manual transmission cars as the increase in power was not seen until 7000rpm, which was the redline for automatic transmission equipped cars. The rear spoiler and tail lights were also redesigned. The Type RZ model was now equipped with larger brake rotors as well as 17 inch BBS wheels.

RX7Series 8 (January 1999– August 2002) was the final series, and was only available in the Japanese market. More efficient turbochargers were available on certain models, while improved intercooling and radiator cooling was made possible by a redesigned front fascia with larger openings. The seats, steering wheel, and instrument cluster were all changed. The rear spoiler was modified and gained adjustability on certain models and the performance models were sold with upgraded brakes offering an improved ABS system.

Mazda has made several references to a revival of the RX-7 in various forms over the years since the RX-7 was discontinued.

In 2012 there was some indication that Mazda was working on a 16X based RX-7.

2015’s Tokyo Motor Show had the unveiling of the RX-Vision concept car utilizing a new rotary engine.

2017 could be the time to introduce a production ready concept, marking 50 years since the revealing of Mazda’s first rotary-powered sports car, the Mazda Cosmo. Maybe we will soon see an RX-9.